for sure
8 synonyms and 2 antonyms for for sure, grouped by meaning and by how common each one is.
Adverb — Without any doubt; certainly.
Synonyms
Everyday swaps
Common words most readers know — safe in any writing.
Less common
Still standard English, but they carry more weight.
Rare, literary or technical
Precise, but they will stand out — check the sense before using one.
Synonyms by Meaning
1. adverb informal
Without any doubt; certainly.
“I can't say for sure whether the shop is open on Sundays.”
Opposites
2. interjection informal
Used on its own to agree with someone or accept a request.
“"Can you send it over tonight?" "For sure."”
How to use for sure
The word patterns that sound natural to a native speaker.
Conversational. As an interjection it is especially common in North American and Australian speech; formal writing uses certainly or with certainty instead.
Frequently asked questions
What is the difference between for sure and surely?
For sure means with certainty and usually attaches to knowing or saying — "I don't know for sure". Surely expresses the speaker's expectation or appeal for agreement — "surely he told you?" — and in American English can also mean certainly.
Is "for sure" too casual for work emails?
As a one-word yes it is fine among colleagues but reads as offhand to clients or senior staff. Certainly, of course, or a plain confirmation of what you will do is safer in external correspondence.